Aircraft propulsion



Patented June 25, 1940 UNITED STATES 2,205,625 AIRCRAFT PaorULsroN Otto Mader, Dessau-Ziebigk, Germany, assignor to Junkers Flugzeug-und-Motorenwerke Akl tiengesellschaft, Dessau, Germany Application August 12, 1935, Serial No. 35,748

4 Claims.

This invention is directed to the regulation of variable pitch propellers, and is more particularly directed to means for adjusting the blades of automatic variable pitch propellers of the con- 5 stant speed type to pitches at low engine speeds greater than the pitches which would be given ordinarily by the automatic blade adjusting mechanism.

Variable pitch propellers which are constructed to vary automatically the pitch of their blades in order to keep the engine speed substantially constant under different iiying conditions for any setting ofthe throttle valve for the engine are well known. It has also been known' to provide l5 a connection between the engine throttle and the propeller that will alter the performance for the pitch changing mechanism for the propeller upon a change in the setting of the throttle. These constructions allow an increase of blade pitch proportional for all motor speeds, so that a motor running at, its lowest speed has its blades set to their minimum pitch. Under this condition, the motor races when the throttle is moved to increase the engine speed, as the automatic blade adjusting means lags in operation behind changes in the engine speed, and the low pitch of the propeller blades creates very little load upon the engine. Such racing of the engine is undesirable.

It is an object of this invention to regulate Another object of the invention is to regulatel a hydraulic system controlling the pitch of propeller blades so that the blades do not reach a minimum pitch which would correspond to the 45 minimum engine speeds. i

Another object of the invention is to provide means for controlling the automatic pitch varying mechanism of the propeller from the engine throttle means so that operation of the engine 5o throttle for certain engine speeds only will automatcally prevent the blades of the propeller from taking the pitch they would ordinarily assume for such speeds.

Generally these objects of the invention are obtained by linking the automatic mechanism Germany August 1'1, 1934 (Cl. T10-135.6)

for varying the pitch of the propeller blades with the engine throttle controls for the engine so that when the throttle controls are set for low engine speeds, the linkage with the propeller mechanism will adjust the mechanism either to 5 keep the blades at a certain minimum pitch, or. will positively adjust the blades to an increased pitch. This desired pitch is greater than that normally corresponding to the low engine speed, and consequently the engine will not race when 10 the engine is accelerated. Preferably a governor controlled hydraulic system is used as the pitch varying mechanism,A and the throttle is connected to the mechanism in such a way as to vary the influence of the governor onv the hy- 15 draulic system. f

The means by which the objects of the invention are obtained are more fully described with reference to the accompanying drawing, in which:

Fig. 1 is a diagrammatic side elevational view\ showing one form of the invention; and y Fig. 2 is a similar view showing a moded form of the invention.

In Fig. l, propeller shaft I` coming from an g5 engine (not shown) is joined to hub 2 of propeler 4. Hub 2 has an extension I0 which supports the mechanism for varying the Ditch of the blades of propeller 4.

This mechanism is a governor controlled hy- 30 draulic system joined tov the propeller so that a variation in engine speed influences the mechanism to increase or reduce the pitch of the propeller blades to place a greater or less, as the case may be, load upon the engine so that an equilibrium between propeller and engine is maintained to keep the engine speed constant. Thus the blades of propeller 4 are rotated by gear 3 which, through arm 6 and link 1, is pivotally connected to rod 40 of piston 42 mounted in o chamber 4|. l

Fluid pressure for the operation of piston 42 is created by any suitable means as by the hydraulic pump joined by, pressure line 5I to valve chamber 46- which communicates with 45 piston chamber 4| through ports 56 and 51; Return lines 52 and 53 extend from opposite ends of chamber 46 back to pump 50. A pressure relief valve 55 is inserted between lines 5l and 52.

Slide valve piston 45 is mounted within cham- 50 ber 46. Piston 45 has`- a relatively thin center portion so that fluid from line 5| `can pass around piston 45 into either port 56 or 51, depending on the position of piston 45 in chamber 46.

Valve 45 is connected by rod 28 and collar 29 55 to the governor which includes bell cranks I2 pivotally joined to frame 2II mounted on extension III. The free ends of bell cranks I2 carry weights I2 while the other ends bear against collar 29. Spring I4 is supported between collar 29 and stop I 6, which stop is normally held in one fixed position. As this mechanism rotates with the propeller, weights I3 will cause the piston 45 to be moved until the centrifugal force of the weights is balanced by the compression of spring I4. Movement o piston 45 will allow fluid to enter into either port 56 or 51, thus causing piston 42 to move and adjust the pitch of the propeller blades so that the engine speed is increased or decreased, as the case may-be.

Ii the engine is slowed to idling speed, the governor without additional control, will adjust the propeller blades to their minimum pitch. At such point, the propeller creates very little load upon the engine aii'd the engine will race when thc throttle is opened to accelerate the engine, as there is a lag between the engine speed, the response of the governor, and the actuation oi the hydraulic mechanism to increase the pitch of the propeller blades. While it is therefore desirable to prevent the blades from taking this minimum pitch position at low engine speeds, the preventive means is preferably connected to the throttle controls and automatically operable thereby,'a's an aircraft pilot would scarcely have time to make a separate adjustment in an emergency.

To accomplish this automatic control, a lever system, operable by the throttle, is provided for altering the tension on the governor spring I4, and at the same time diverting the fluid pressure from valve chamber 4S, so that the piston 42, and therewith the pitch of propeller blades 4, is kept immovable upon the movement of the throttle to slow the engine below a predetermined speed.

For this purpose, stop I6 is Joined to lever I1,

this lever being pivotally connected at Il adjacent one end to frame 20, and being movably joined at I 3 torod 22 which in turn is connected to ring 23 fitted in collar 25 which is axially slidable along the nose 24 of the motor housing. Collar 25 is connected to rod 21 which passes through bore 26 in the motorhousing to connect with lever 30, which in turn is connected at one end 32 to rod 35 joining throttle lever 34 to valve 36 mounted within intake manifold 3B. Fuel is supplied from carburetor 31. The position of lever 34'can be fixed through pawl 42 engaging teeth 44. For varying the degree of movement of rod 21, lever 30 is connected at its other end 3i to -lever 33 having pawl 4I engaging teeth v43. It is noted that lever 33 will permit rod 21 to be ad- 'justed independently of movement oi lever 34.

End 2l of leverl I1 is extended beyond pivot I8.

" This end I8 is adapted to contact rod 6I of by- Vpass valve 60 inserted between pressure line 5I and return line 53 of pump 50. In normal operation end 2l is spaced from rod 6I, but for predetermined movements of throttle 34, contact is made to disconnect pump 5l from valve chamber 46, and thus rendering piston 42 inoperable.

' In operation, movement of lever 34 changes the tension on spring I4 through the change in position of stop I5. As the tension of spring I4 is selected to keep the engine speed constant by means of the pitch ofthe propeller blades, diiferent constant speeds are permissible by the changing of the position of stop i6. As the throttle lever 34 is moved to the right as seen in Fig. 1, the point will be reached when the lever has just barely touched the rod 6l, and the governor has reset the pitch of the propeller blades to correspond to the engine speed at that position of the throttle valve.. ,Further movement of lever 34 to the right will reduce the speed of the engine to idling speed, or to a speed at which the blades are to have an unvaried pitch. This further movement of the throttle causes end 2i of lever I1 to push rod 6I to open by-pass valve 40, and thus no hydraulic pressure exists to move piston 42 from the position it held at the time the by-pass valve was opened. Consequently, the engine at idling speeds has its propeller pitched for higher speeds, and when the engine is accelerated by pulling the throttle to the left the load produced A by this propeller pitch prevents the engine from racing. Thus the minimum pitch assumed by the propeller blades is limited to the pitch of a. normal rigid propeller, or if desired, to a somewhat higher pitch. The range of regulation of the governor by the throttle lever 34, and the point at which movement of lever 34 actuates rod 6I can be changed by shifting lever 33.

In Fig. 2 an apparatus is shown which positively increases the pitch of the propeller when the throttle 34 passes a predeterminedV point in the reduction of the fuel supply to the engine. Instead of employing ahy-pass valve as in Fig. l, rod 28 of piston 45 is extended through spring I4, stop I6, and lever I1 by rod 63 which terminates in an enlarged portion 64. Stops 1I and 12 are fastened to rod 40 .of piston 42, and by-pass valves 65 and 66, operable respectively by stops 1I and 12, create communication between piston chamber 4I and return lines 52 and 53. Valves 65 and 6G are provided with extensions 61 and 6B, respectively, which act as abutments for stops 1I and 12. The remaining portions of the apparatus are similar to those described for Fig. 1.

When the throttle is moved to slow the engine, and passes the position beyond which the propeller blades are not to be reduced in pitch, piston 45 is moved to the right in Fig. 2 by the lever I1 engaging portion 64. Fluid enters chamber 4I to thrust piston 42 to the ien. and" thereby the pmpeller blades are given a pitch greater than they would be given by the governor at that speed, or the speed at which the engine runs just before lever I1 engages portion 64.

Stops 1I and 12 can be placed on rod 40 to lim- V it the movement of piston 42, and thus limit the degree of pitch change in the blades. For example, when stop 12 engages valve 66 through extension 68, further movement of the valve to the left is prevented by the by-passing of the fluid under pressure from pump 50, to return line 53 through valve it. Thus the pressure from the pump is rendered ineiective to give further movement to piston 42, and the pump does not need to create the undesirable high pressures necessary to operate safety valve 55.

AThe invention therefore provides means for automatically varying the propeller blade pitch so that constant engine speeds are maintained for corresponding throttle settings, except when the throttle is moved to reduce the engine speed below a predetermined value, at which time the pitch is automatically rendered unchangeable, or is positively increased, and danger of the engines racing on sudden acceleration from low speeds is avoided. While the invention is especially advantageously used with hydraulic pitch changing and mechanically operated variable pitch pro- Y pellers.

Having now described a means by which the objects of this invention may be obtained, what I claim as newvand desire to secure by Letters Patent is:

1. in apparatus for controlling a constant speedpropeller driven by an engine comprising governor means, including Aspeed responsive means, for varying the pitch of the propeller blades, an engine throttle, means interconnecting said throttle and said speed responsive means for varying said speed responsive means and the con stant speed setting of the propeller blades upon throttle movement, means responsive to move-- ment of said interconnecting means for maintaining the propeller blades at .a constant pitch when said throttle is moved toward closure a predetermined amount, -and means for varying the speed responsive means and the position of said movement responsive means relative to said throttle so as to vary the position of the throttle which maintains the propeller at the said con-v stant pitch when the throttle is moved toward closure.

2. An apparatus for controlling a constan speed propeller driven by an engine comprising governor means, including a spring, for varying the pitch of the propeller blades, an engine throttle, means interconnecting said throttle and said spring for varying the tension of said spring and the constant speed setting of the propellerv blades upon throttle movement, means responsive\to movement of said interconnecting means for maintaining the propeller blades at a constant pitch when said throttle is' moved toward closure a predetermined amount. 'and means for varying draulic pump, a hydraulic motor connected tosaid pumpand adapted to turn the propellerv blades, and a governor operated valve interposed between said p'ump and motor; and said movement responsive means comprising a by-pasa valve interposed between said pump and governor operated valve, and means for operating said ley-pass valve by said interconnecting means.

4. An apparatus as in claim 1, said governor and speed responsive means comprising a hydraulic pump, a hydraulic motor connected to said pump and adapted vto turn the propeller blades, and a governor operated valve interposedA between said pump and' motor; and, said movement responsive means comprising at least one by-pass valve interposed between said motorand governor operated valve, and means actuated by predetermined movements of said motor for operating said by-pass valve.

OTTO MADER. 

